Clutches and the like



Oct. 25, 1960 1-. A. BANNING, JR 2,957,964 I V CLUTCHES AND THE LIKEOriginal Filed April 21, 1955 4 Sheets-Sheet 1 IN V EN TOR.

ThomosA. Bonning,dr.,

mpW.

Oct. 25, 1960 T. A. BANNING, JR 2,957,964

CLUTCHES AND THE LIKE I Original Filed April 21, 1955 4 SheetsSheet 2INVENTOR. ThomosABonningAn.

Oct. 25, 1960 T. A. BANNING, JR 2,957,954

CLUTCHES AND THE LIKE Original Filed April 21, 1955 4 Sheets-Sheet 4INVENTOR.

Thomas A. Banning, dr.,

United States Patent "ice CLUTCHES AND THE LIKE Thomas A. Banning, Jr.,5520 South Shore Drive, Chicago, 111.

Original application Apr. 21, 1955, Ser. No. 502,947,

now Patent No. 2,856,692, dated Oct. 21, 1958. Divided and thisapplication Oct. 15, 1958, Ser. No. 767,396

7 Claims. (Cl. 200-98) This invention relates to improvements inclutches, and the like. By this term I mean devices by which twoadjoining shafts or other rotary elements may be connected together fordrive of the one by the other, or may be disconnected from each other sothat the driving element may rotate in either direction withouttransmission of rotary drive to the other or driven element. In theformer case of eifecting drive from the driving element to the drivenelement the two elements are clutched together; in the latter case ofdiscontinuing drive from the driving element to the driven element thetwo elements are unclutched from each other. Numerous forms of clutcheshave been developed, generally to meet specific conditions of operationimposed by the form and intended use of the machine wherein they areincluded.

Primarily the clutch construction herein disclosed is intended for usein instrumentation units wherein very close tolerances of accuracy ofmeasurements of angular rotations are a requirement. Thus, inmeasurements of distance by integration of successive relatively smallincrements of the total distance, with intervening distance elementswhich are not to .be included in the totalizing of the numerousincrements, it is evident that even slight losses of measurement orslight unintended additions of distance to the integration of theintended increments, will produce serious over-all errors ofintegration. Such errors may and in various kinds of operations will besufficient to make the entire measuring operation worthless.

The herein disclosed clutch construction is one in which the clutchingand unclutching operations are produced by direct movement of a drivinganad driven element towards and from each other. The engaging surfacesof these elements are friction annuluses having their planar surfacesnormal to the axis of rotation. It is evident that the torquetransmitting ability from driving to driven element is limited by thediameters of the contacting surfaces, the conditions of the contactingsurfaces, the materials from which such surfaces are formed,

and the pressure produced between the contacting surfaces. In thisarrangement provision must be made for producing continuity of suchengagement between the driving and driven surfaces at the neededpressure. When such engagement is produced by direct magnetic pullexerted between the elements, and when such magnetic pull is developedby a solenoid electrically energized, it is generally necessary toretain cur-rent on the magnetizing coil or coils during the interval ofengageengagement producing Patented Oct. 25, 19cc engagement between thedriving and driven elements, together with supplemental magnetic meansto retain the driving and driven elements in driving engagement witheach other until a contrary disengaging force is producedelectromagnetically. Thereupon such holding magnetic force is broken andthe disengagement occurs.

The supplemental magnetic means referred to in the preceding paragraphis conveniently in the form of permanent magnet elements which areconnected to the movable driving or driven element and are adapted tocome into magnetic holding engagement with stationary abutment elementswhen the clutching or unclutching movements occur. Thus once suchpermanent magnet elements have thus engaged such abutments the desiredholding force is produced, and it is not then necessary to maintain thecurrent supply for the electromagnets, and such current supply may thenbe discontinued until a contrary shift of the driving or driven elementis to occur. Thereupon another electromagnetic releasing force isproduced by which the engagement of such permanent magnet element isbroken, and the engagement between the driving and driven elements isterminated. Thus, only a short impulse of current is required to producethe engagement (or disengagement) of the driving and driven elementswith (or from) each other. Thus the numerous clutching and unclutchingoperations are produced without need of maintaining current on amagnetizing coil during the long intervals which may interpose betweensuccessive engagements and disengagements of the driving and drivenelements, with or from each other.

It is a further object of the invention to provide a clutch unit whereinsimilar operations are employed for producing the disengaging operationsof the driving and driven elements so that it is not necessary to retaincurrent on any magnetizing coil for more than a very short interval oftime.

A further feature of the invention relates to provision of a clutch unitof the foregoing type wherein, when the driving and driven elements aredisengaged from each other the driven element will be immediately lockedsecurely against rotation until a subsequent clutching impulse or signalarrives to produce such clutching action. According to the structurewhich is provided to accomplish this purpose, I have provided an elementwhich is drivingly connected with the output or driven shaft and isaxially shiftable a. slight distance axially between the driving anddriven shaft locations. The driving shaft carries a friction diskelement lying in a plane normal to the axis of rotation, and there is astationary element located near the driven shaft location and providedwith another stationary friction disk element also lying in a planenormal to the axis of rotation. The axially shiftable element isprovided with faces on its opposite 'ends, which faces are also normalto the axis of rotation. By shifting such element in the clutchingdirection the face of one of its ends is engaged with the face of thedriving friction disk element to produce drive; by shifting such elementin the unclutching and braking direction the above mentioned face isdisengaged from the face of the driving disk, and the faceon its otherend is engaged with the stationary friction disk element to produce abraking action. The amount of shift needed to effect clutching fromunclutched and braked condition, or vice versa, is very small, of theorder of one or a few thousandths of an inch. 7

In connection with such axially shiftable element I have provided verysimple and elfective shifting means which incorporates the featureshereinbefo're explained. The arrangement is such that a very substantialmultiplication of force is produced from that exerted by the actuatingand holding magnets, to such axially shiftable element. Thus the actualfrictional engagement ofthe axially shiftable element with either thedriving element or the brake element is substantial and much larger thanthe originating force.

This shifting means includes a force originating element which includesa pendulum-like downwardly extending arm to which are connected thearmature and permanent magnet elements by which such arm is swung in theone direction or the other by properly located solenoids carried by thebase plate. This arm carries suitable electrical contacts by which theincoming current impulses are delivered to the one solenoid or theother, and which contacts break engagement with companion stationarycontacts shortly prior to completion of the shift in the one directionor the other. Thus each shift of the axially movable element is producedby a short impulse, with discontinuation of current supply at or shortlyprior to the completion of the shifting movement.

It is a further feature of the invention to provide adjustable meanswhereby the permanent magnet elements may be adjusted after the unit hasbeen assembled, so as to bring them into correct functioning positionwith respect to the pendulum-like arm. These adjustment means includemeans to adjust the permanent magnets towards and away from thependulum-like arm.

It is a further object of the invention to provide spring means toeffect additional frictional engagement of the axially shiftable elementwith either the driving element or the brake element. Such spring meansis so arranged and connected to other elements of the device that atoggle effect is produced acting to develop spring originated force ineither the driving element direction or the braking element direction,with passage of the spring effect through a force reversing location inaccordance with the action of conventional toggle actions. Thearrangement is such that the spring force developed by this supplementalelement may be adjusted without disturbance to other elements of thedevice. Such spring toggle force acts to supplement the holding forcedeveloped by the permanent magnets when the shiftable element reacheseither terminus of its movement.

Other objects of the invention are to provide a very compact and wellordered arrangement of the essential parts, to produce a rugged anddurable device, to produce a very quick acting clutch, and to produce anarrangement of simple construction which will not readily get out oforder. Also, to produce a clutch unit having a strong specific holdingpower, that is, a large holding power per unit weight of the device,with corresponding high specific torque transmitting ability. Also, toproduce a clutch unit which can be built at low cost, from parts readilyproduced by conventional shop practices, and with comparatively smalllabor needed for assembly.

Other objects and uses of the invention will appear from a detaileddescription of the same, which consists in the features of constructionand combinations of parts hereinafter described and claimed.

This application is a division of my co-pending application for LettersPatent of the United States for improvements in Measuring and RecordingVarious Well Drilling Operations, Serial No. 502,947, which becameLetters Patent No. 2,856,692, issued October 21, 1958.

In the drawings:

Figure 1 shows a front elevational view of the clutch embodying thefeatures of the present invention;

Figure 2 shows an end view of the clutch illustrated in Figure 1,looking at the left-hand end of such clutch;

Figure 3 shows a longitudinal section through the clutch design shown inFigures 1 and 2, the shifter element being shown in its right-hand movedor driving position, the braking element being disengaged to permitrotation of the said element and thus to also permit rotation of thedriven shaft; and in this figure the permanent magnet, such as an Alnicomagnet, at the left-hand side of the unit is shown in engagement withthe stationary armature to which it magnetically locks at conclusion ofshift in the direction to carry such permanent magnet into engagementwith such armature, so that the clutch will be retained in its thusshifted position without need of continued energization of the shiftingmagnet; and

Figure 4 shows a cross-section taken on the line 4-4 of Figure 3,looking in the direction of the arrows; and this figure shows that theshifter yoke by which the clutching element is shifted back and forth isitself pivoted to the operating yoke for rock about an axis above theaxis on which the operating yoke rocks, to thus produce a strongshifting action on the shifter yoke by exertion of a much largershifting force on the operating yoke; and in this figure I have alsoshown the supplementary spring toggle element by Which the holdingactions in either direction of shift are augmented.

Figures 1, 2, 3 and 4 show in detail and on enlarged scale as comparedto an actual unit the construction of this permanent magnet (Alnico)type of clutch. This unit includes the U-shaped frame element 215 havingthe base portion 216 which sets directly on the plate 67, and alsoincludes the upwardly extending bracket arms 217 and 218. The drivenshaft 219 extends from the left-hand side of the unit to a locationbetween the bracket arms, and the driving shaft 220 extends from theright side of the unit to a location between the bracket arms, and toproximity to the end of the driven shaft. These two shafts areaccurately aligned with each other. The driven shaft is supported andjournalled by the ball bearing 221 having its outer raceway 222 seatedinto a collar element 223 which is set down into a semi-circular recesson the top edge of the bracket arm 217. This collar element is providedwith the outwardly extending flange 224 which bears against the outerface of the bracket arm and is secured thereto by the screws 225. Ahearing retainer ring 226 is also clamped against the outer end of theouter raceway 222 by these screws. The driven shaft is provided with theflange 227 which engages the inner raceway of the ball bearing, 228, tolimit the inward movement of said shaft; and a cup-shaped element 229 isset onto the shaft just to the inside end of the inner raceway to fixthe shaft against outward withdrawing movement through the hearing.

The driving shaft 220 is journallecl in the ball bearing 230 seated in asuitable opening of the right-hand portion of the unit. To this effectthe outer raceway of this ball-bearing is seated into the collarelements 231 with its outer raceway carried by such collar element inmanner similar to the construction shown for the bearing of the drivenshaft. This collar element is therefore set down into a semi-circularrecess formed in the top edge of the bracket arm 218, and the flange 232of this collar element sets directly against the outer face of thebracket arm 218 to which it is secured by the screws The inner end ofthe driving shaft is enlarged as shown at 234 to establish an abutment.The disk element 235 is then set onto the inner end of the shaft andagainst this abutment; and a key lug 236 of the shaft engages a suitableslot of the disk to key the disk to the driving shaft. Thus the disk anddriving shaft are rotatably connected together.

The disk 235 is provided with a rightwardly extending neck 237 whichengages the inner end of the inner raceway 238 of the bearing 230, and acup-shaped element 239 engages the outer end of the said inner racewayto retain the shaft properly against inward shift through the ballbearing.

The sleeve 240 is splined onto the driven shaft by engagement of the pin241 which extends through such sleeve into engagement with the axiallyextending keyway 242 of the shaft. Although only a small shiftingmovement of the sleeve on the shaft is to be executed, as will presentlyappear, still the sleeve is made of ample length as shown in Figure 3 toensure accurate operation of the sleeve during its shift on the shaft.The lefthand end portion of this sleeve is provided with the outtwe t'Wardly extending flange 243 of considerable diameter and facialbearingsurface. A ring plate 244 is set onto the inner end portion of thecollar element 223, preferably by a threading arrangement as shown, sothat by turning this ring plate its inside face may be advanced towardsor retreated from the position of the flange (when said flange is in oneof its two intended positions of operation). A set screw 245 is extendedradially in wards through the ring plate and into locking engagementwith the collar element to lock said ring plate in its adjustedposition.

Preferably the flange 243 is of slightly greater diameter than the ringplate and is slightly recessed in its outer face to receive the ringplate 244 during one intended operation. A facing of brake lining orother friction material 246 is cemented or otherwise adhered to the faceof the flange 243, such facing being of ring shape as evident fromFigure 3. The flange 243 is accurately formed and set onto the drivenshaft so that the plane of such friction material face is normal to theaxis of rotation, and likewise the ring plate 244 has it right-hand facenormal to the axis of rotation. The parts are accurately made so thatwhen the sleeve 240 is shifted .leftwardly a small distance an evenengagement of the friction material (and element 243) occurs with thering plate to lock the parts, including the driven shaft, againstrotation.

The sleeve 240 also carries a cup-shaped element 247 which is drivinglyconnected to such sleeve by the key and keyway shown at 248; and a cupelement 249 is set onto the shaft to the right of the concave inner faceof such element 247 to retain such element in place. This cup element isprovided with the peripheral flange portion 250 providing an annular orring shaped portion facing the disk element 235. Said disk element ispreferably of slightly larger diameter than said flange 250 and isfacially recessed slightly to accommodate the flange 250 during oneintended operation. A ring of brake lining or other friction material251 is cemented or otherwise secured to the face of the disk element235; and the parts are accurately formed with surfaces lying in planesnormal to the axis of rotation.

The proximate portions of the cup-shaped element 247 and the flange 243are so spaced and formed as to provide space to accommodate a shifterelement, presently to be described. It is here noted, however, that whenthe sleeve 240 is shifted rightwardly into the position shown in Figure3 the flange element 250 is brought into driving engagement with thedisk element 235 so that drive from the shaft 220 to the shaft 219 iseffected. On the other hand, by a slight shift leftwardly the flange 250'will be withdrawn from engagement with the disk element to discontinuedrive from the shaft 220 to the shaft 219, and immediately thereafterthe flange 243 will be brought into frictional engagement with the ringplate 244 which is stationary, thus locking the sleeve 240 stationaryalso. Since the shaft 219 is drivingly connected to such sleeve itfollows that said shaft will also be thus locked stationary at suchtime.

The clearance between the shifting faces of the flange 250 and thefriction material carried by the flange 243 are such that only a slightshift of the sleeve is needed to effect the change from the driving ofthe shaft 219 -to the locking of said shaft stationary. I shall nowdescribe the shifting means to produce these effects:

A ring 252 is seated on the sleeve 240. Thisring 'conveniently comprisesthe inner raceway of a ball bearing of which the outer raceway is shownat 253. A semicircular yoke element 254 is provided (see Figures 3 and4), such yoke being provided with an upwardly facing semi-circularrecess to receive the lower half of the ring 252. The flange 243 and thecup shaped element 247 are both so formed that shift of the ring 252 inthe one direction or the other will produce engagement of such ring withsuch element 243 or 247 as the case may be, with- 6 outengagement of theouter raceway 253 with such element 243 or 247; But the ring 253 isengaged by the yoke member. Consequently rotation of the sleeve and theinner ring 252 or inner raceway of the ball hearing may freely occursubstantially without friction since the outer raceway of the ballhearing may remain non-operative, being seated into the yoke. Thus theback and forth shifts of the yoke are effected carrying with such yokethe sleeve and its engaging surfaces.

There is another actuating yoke 255 of larger span than the yoke 254 andextending below and up at the sides of the yoke 254 (see Figure 4). Thearms 256 and 257 of this larger yoke embrace the yoke 254 between them,and the depth of the yoke 255 is suflicient to permit free relativemovement between the two yokes. U-shaped horizontal bars 258 and 259 areset against the front and back edges of the bracket arms 217 and 218,and secured to said bracket arms by the screws 260 as indicated inFigure 2. Thus a rigid frame is provided; and additionally said barsextend up far enough to provide supports for the yoke 255 as follows:

The pivot pins 261 and 262 are extended through the bars 258 and 259respectively, the inner ends of such pins being tapered to fit intocorresponding tapered recesses in the two arms 263 and 264 of said yoke255. Lock nuts 265 and 266 are set onto these pivot pins for theself-evident purpose. Examination of Figure 4 will show that thehorizontal plane which includes the shafts 219 and 220 lies above thehorizontal plane which includes the pins 261 and 262. The upper portionsof the opposite sides of the yoke 254 are pivotally connected to thearms 263 and 264 of the yoke 255 by the pins 265 and 266 which lie inthe horizontal plane which includes the two shafts 219 and 220. It willnow be apparent that rock of the yoke 255 about its axis of support willresult in a slight shift of the axis extending through the two pins 265and 266, in direction opposite to that in which the lower portion of theyoke 255 is shifted. Since the yoke 254 is connected to the yoke 255 bythe pins 265 and 266 such yoke 254 is allowed to shift directly in onedirection or the other while remaining parallel to itself during suchshifts, that is, remaining within a plane nor- ,mal to the axis of theshafts 219 and 220. Due to the fact that during such a shift the pins265 and 266 will travel parallel to themselves and within a cylindricalsurface of which the axis is coincident with the axis passing throughthe two pins 261 and 262, it follows that such rock of the yoke willproduce a very slight vertical component of motion of the yoke 254.However, due to the slight angular shift which will be executed by theyoke 255 and the small distance between the pins 262 and 266 (and 261and 265) it follows that no appreciable vertical component of motionwill be produced, such as above suggested. Any slight vertical componentof movement may be accommodated by slight clearances between the parts.

It is now evident that rock of the lower portion 267 of the yoke 255will serve to produce the desired shifts of the sleeve 240 and connectedparts, such sleeve shifts being in direction opposite to that ofmovement of the lower portion 267 of the yoke. such an arrangement willproduce a large multiplication of force as between that applied to theyoke portion 267 (and the extension thereof, 269) and that produced atthe braking or driving position of the sleeve elements. This fact isevident from the fact that the distance be;- tween the pins 262 and 266is several times smaller than the radius of swing of the yoke extension269. It is thus possible to produce the desired gripping forces betweensurfaces by use of comparatively small forces applied to the yokeextension 269. The yoke shifting and holding means is as follows:

Referring to Figure 3, the plates 268 and 269 are secured to theopposite faces of the yoke portion 267;

These plates are separated from each other and produce It is alsoevident that a slightly stiff but yieldable downward extension of theyoke portion 267. Blocks of magnetic material, 270 and 271 are securedto the lower end portion of this downward extension. Thus the yoke maybe shifted back and forth by production of proper magnetic fields toinfluence and act on such blocks. The strong solenoids 272 and 273 areset against the inside faces of the arms 217 and 218 and are clamped insuch positions by screws 274 passed through retainer plates 275 and 276as shown in Figure 4. These solenoids are of the air-core type in thesense that they are not provided with conventional magnetic materialcores. However, blocks of strongly magnetized high permeability and highretentivity material, such as Alnico metal, are located and securedwithin the air core spaces of these solenoids. These are the blocks 277and 278 secured to the inner ends of the screws 279 and 280. Thesescrews are threaded through the screw plugs 281 and 282 of large enoughsize to allow the Alnico blocks to be inserted into place when suchplugs are removed; and lock nuts 283 and 284 are threaded onto theprojecting ends of the screws as shown in Figure 3. By this arrangementit is possible to adjust each Alnico block to exact position within theair core of its corresponding solenoid.

With this arrangement the following operations are possible:

Assuming that the yoke has been shifted to one extreme position, asshown in Figure 3, the block 270 of magnetizable material has beenmagnetically gripped by the Alnico block 277; and at the same time aconsiderable air gap exists between the block of magnetizable material271 and the Alnico block 278. Accordingly, a strong holding force isbeing exerted to retain the yoke in its position of shift shown inFigure 3. During this operation it is assumed that there is no currentflow through either solenoid. Upon energizing the solenoid 273 toproduce a strong magnetomotive force a suflicient pull will be developedby such solenoid on the magnetizable block 271 to pull said block andthe block 270 free of the holding force exerted by the Alnico block 277,and immediately the yoke will be drawn towards the right far enough toengage the Alnico block 278 with the magnetizable block 271. Having donethis, such Alnico block 278 will retain the yoke in its newly shiftedposition Without need of further energization of the solenoid.Accordingly the current may now be shut on from such solenoid 273leaving the parts locked in their new position.

It is noted that the downward extensions 268 and 269 are formed ofsomewhat flexible springy steel or the like, so that they may flexslightly to permit the Alnico blocks to come into full contact with themagnetizable blocks 270 and 271, or vice versa, after the sleeve hascompleted its necessary shift to produce either braking action ordriving action as the case may be.

The impulses of current needed to excite the solenoids are delivered tosuch solenoids by the microswitch contacts or the contacts of the switchby which delivery of the impulses to the clutch are controlled. Varioussignalling arrangements incorporating these switching features aredisclosed in Letters Patent, No. 2,671,346 issued to me March 9, 1954and in said parent application, Serial No. 502,947, Patent No.2,856,692, of which case this application is a division. Thus it is notdeemed necessary to describe them in detail here. However, it is nownoted that the form of clutch now being described includes in itselements contacts by which the currents sent to the solenoids 272 and273 are cut off prior to completion of the full actuating movements sothat the yokes movements are produced by the desired current impulseswithout need of sustaining such currents. To this end, the flexible leaf285 is connected to the lower portion of the downward extensioncomprising the thin plates 268 and 269, such connection including theinsulating elements 286 and 287. The blocks of insulating material 288and 289 are supported by the floor of the frame of the switch andclutch. Studs 290 and 291 are extended through these insulating blocks;and the contacts 292 and 293 are carried by the inner ends of the studs.The lower ends of the leaf 285 carries complementary contact elements294 and 295. By setting the studs back and forth in the insulatingblocks to correct positions of adjustment it is possible to bring aboutcontacting functions which will produce the desired circuit opening andclosing operations. These operations include the following:

With the parts in the positions shown in Figure 3 the contacts 294 and292 being engaged, a circuit is established which includes the solenoid273, and, for example, the micro-switch stationary contact for one ofthe positions of the control microswitch. On the assumption that saidmicroswitch was at the time in that positon so that its stationarycontact corresponding to the contact 292 was not in engagement with theleaf contact of such microswitch, it is evident that the solenoid 273would remain energized so that the clutch would remain in the positionshown in Figure 3. Then, as soon as the microswitch was caused toreverse its leaf contact its stationary contact in connection with thesolenoid 273 would be engaged, thus closing the circuit through suchsolenoid 273 and immediately reversing the clutch position. Shortlyafter commencing the clutch reversal the leaf 285 (see Figure 3) wouldcarry the contact 294 away from the contact 292, thus opening thecircuit of the solenoid, notwithstanding that the control microswitchmight remain in its then position for a long time. Such opening of thecircuit for the solenoid 273 should occur at a time when the leaf andyoke had moved substantially half way to their new positions, and wherethe force of the Alnico block 278 would be large enough to complete thethrowing movement, and to bring the magnetizable block 271 intoengagement with the Alnico block 278 to thus retain the yoke andconnected parts in their shifted positions. But it is noted that duringthese operations the contact 295 carried by the leaf 285 will come intoengagement with the contact 293 in good time to thus establish a partialcircuit of which the solenoid 272, the opposite contact of themicroswitch controlling the operations, and the contacts 295 and 293thus brought together would comprise portions. This circuit would,however, not be completed until reversal of the leaf contact of thecontrol microswitch, so that the clutch reversing operation would bedelayed until such control microswitch should reverse its position. Whensuch control microswitch reversal should afterwards occur the clutch ofFigure 3 would reverse its position, with change of its contacts inharmony with the principles of operation just explained.

The Alnico or other permanent magnet arrangement above described willserve to ensure retention of the yoke in its shifted position and underthe degree of force developed by the design of the parts. In case itshould be desired to produce further holding effects than those due tothe Alnico magnets, spring toggle elements may be provided which are asfollows:

The yoke 255 is shown in Figure 4 as being provided with the heels 296and 297 to which are connected the downwardly extending stiff pins orrods 298 and 299. Accordingly these rods will rock or swing as pendulumsduring the rocks of the yoke, such pendulum movements of the rods beingexecuted about the horizontal axis through the pins 261 and 262 inFigure 4. Secured to the base portion of the unit and directly beneaththe aforesaid axis of rock are the two upwardly extending pins 300 and301 which are adjustably secured to the brackets 302 and 303. Theproximate ends of the rods 298 and 299, and of the pins 300 and 301 areprovided with abutments between which the compression springs 304 and305 are contained. During rock of the yoke in either direction the rods298 and 299 will swing through their lines of registry with thecorresponding pins, the

springs being compressed as the rods approach such registry, and suchregistry points being dead-center positions. Having passed suchdead-center positions the springs will exert their expanding forces tocomplete the swing of the yoke, and to retain the sleeve and itsconnected parts in their shifted positions. By adjustment of the pins300 and 301 it is possible to produce the desired spring force efiects,taking into account also the characteristics of the springs.

Examination of Figure 3 will show that the plugs 281 and 282 are formedof non-magnetic material. Also that the plates 268 and 269 are connectedto the central portion of the yoke 255 by a block of non-magneticmaterial 306. These nonmagnetic carriers ensure protection of drainageof magnetic effects through short circuits, and thus assure productionof the maximum magnetic moving and holding effects possible.Conveniently, the element 306 comprises a portion of the yoke 255 inwhich case said yoke comprises non-magnetic material in its entirety.

It is noted that in Figures 1 and 3 the driving shaft is shown at theright and the driven shaft at the left.

I claim:

1. -In a clutch, the combination of aligned input and output shafts,means to journal said shafts in alignment with each other and with theirproximate ends adjacent to each other, a driving element secured to theend portion of the input shaft and provided with a driving surfacefacing towards the output shaft, a stationary brake abutment adjacent tothe output shaft and provided with a braking surface facing towards theinput shaft, an engaging element mounted on the output shaft between thedrive element of the input shaft and the stationary brake abutment andaxially movable on the output shaft between a first defined drivingposition and a second defined braked position and drivingly connected tosaid output shaft during such axial movement thereon, said engagingelement including a driven surface facing the driving surface of thedrive element and proximate to said driving surface, and including abraking surface facing the braking surface of the stationary brakeabutment and proximate to said stationary brake abutment surface, theengaging element being movable on the output shaft between the firstdefined driving position wherein its driven surface is in drivingengagement with the driving surface of the drive element with itsbraking surface non-engaged with the braking surface of the stationarybrake abutment, and the second defined braked position wherein itsbraking surface is engaged with the braking surface of the stationarybrake abutment and with its driven surface non-engaged with the drivingsurface of the drive element, together with means to shift said engagingelement between said first defined and second defined positions, saidmeans including a pair of solenoids having their exciting coils mountedsubstantially in axial alignment with each other and separated axiallyfrom each other to provide an armature space between said coils, anarmature comprising a block of magnetic material located in said space,means to movably mount said armature in said space, said meanspermitting movement of the armature towards one solenoid coil to a firstdefined armature position and permitting movement of the armaturetowards the other solenoid coil to a second defined armature position,and including operative conneotion between said armature and theengaging element constituted to shift the engaging element to its firstdefined driving position when the armature shifts to its first definedarmature position and to shift the engaging element to its seconddefined braked position when the armature shifts to its second definedposition, together with a permanent magnet corresponding to eachsolenoid and proximate to that end of such solenoid towards which thearmature moves when the coil of such solenoid is energized, in positionfor magnetic engagement with the armature when such armature movestowards such solenoid.

2. A device as defined in claim 1, together with stationary contactelements corresponding to the two solenoids, movable contact elements inconnection with the armature and movable therewith and constituted toengage the stationary contacts selectively according to location of thearmature in said first defined armature position or said second definedarmature position, said movable contacts engaging one stationary contactwhen the armature is in said first defined position and non-engaging theother stationary contact when the armature is in such position, andengaging the said other stationary contact when the armature is in saidsecond defined position and non-engaging the first mentioned stationarycontact when the armature is in such position, and the connections whichdeliver current to the solenoid coils selectively including thestationary contacts, the stationary contact which is engaged by themovable contacts when the armature is in its first defined positionconnecting to the solenoid to which the armature moves to its seconddefined position, and the stationary contact which is engaged by themovable contacts when the armature is in its second defined positionconnecting to the solenoid to which the armature moves to its firstdefined position.

3. A device as defined in claim 2, wherein the movable contactsnon-engage with each stationary contact prior to full movement of thearmature to its terminus of movement in each direction and wherein suchmovable contacts engage with each stationary contact not later thanmovement of the armature to its terminus of movement in such direction.

4. A device as defined in claim 3, wherein the armature is magneticallyretained in each terminal position of its movement by the permanentmagnet corresponding to such terminal position of movement.

5. A device as defined in claim 1, together with means to support eachpermanent magnet in its position proximate to that end of the solenoidtowards which the armature moves when the coil of such solenoid isenergized, including means to adjust the position of such permanentmagnet in direction towards or away from the armature, to thereby adjustthe position of such permanent magnet for engagement by the armatureduring movement of the armature towards the solenoid corresponding tosuch permanent magnet.

6. A device as defined in claim 1, wherein the operative connectionsbetween the armature and the engaging element include a flexible leverarm, connections between one end of said flexible arm and the engagingelement, and connections between the other end of said arm and thearmature, said flexible arm permitting yield thereof for engagement ofthe armature with either permanent magnet after engagement of the drivensurface thereof with the driving surface of the drive element or afterengagement of the braking surface thereof with the stationary brakeabutment surface.

7. A device as defined in claim 6, wherein said lever arm comprises aforce magnifying element from the armature to the driven surface of theengaging element and from the armature to the braking surface of theengaging element.

References Cited in the file of this patent UNITED STATES PATENTS1,222,720 Bijur Apr. 17, 1917 1,853,225 Rae Apr. 12, 1932 1,883,163 VanVoorhis Oct. 18, 1932 2,424,306 Denault July 22, 1947 2,825,823 WoodcockMar. 4, 1958

